The aqueous acid–base titration is one of the most widely used laboratory exercises for a first course in introductory or analytical chemistry. Laboratory experiments give students practical experience and technical competence in manipulation, observation, data collection, processing and analysis of data, interpretation of observations, problem solving, team work, experiment design, and communication and presentation. However, laboratory training is expensive, it requires academic and technical staffing, instruments, consumable materials and laboratory experiments take up a great deal of staff and student time. Simulations can help in developing laboratory skills. Computer simulations offer a learning experience that complements both classroom instruction and traditional laboratory experiences.

With pH Titration Simulator, students can select an acid, its concentration, the concentration of the base, and an indicator to be used in a simulated a titration. They can control the rate at which base is added to the acid from a buret. As the solution’s pH changes, students can see the changes in color for the chosen indicator. After each addition of acid or base, the computer calculates the pH, the concentrations of each of the acidic and basic forms of the indicator, and the corresponding absorption (according to Beer's law), and displays the approximate color of the solution. Students can develop a clear understanding of how changes in pH affect the color that is observed in the solution, the pH span in which the indicator changes its color, and at what pH the major change occurs. This allows students to understand that each particular indicator is useful in detecting changes at a specific pH value. The simulation of several different titrations involving strong and weak acids can complement this, so that students understand the uses of the different indicators that are available. The program also includes a section that introduces students to the theory and use of the pH meter. A detailed understanding of these concepts would necessarily involve a large number of experiments, which may not be feasible in the available laboratory time. Computer simulation provides an extremely versatile way to ensure that students can have experience with a wider variety of indicators and titrations than would be possible in the laboratory. At the end of the experiment, data that are displayed graphically on the computer screen can be stored on disk and reexamined with the aid of spreadsheet software.

A screen from pH Titration Simulator

Acknowledgment

The authors thank Robert de Levie of Bowdoin College for providing the algorithm for the pH calculation and for his advice and suggestions for improving the program.